Burster element for boring type continuous mining machines



March 27, 1956 G. F VON STROH 2,739,798

H BURSTER ELEMENT FOR BORING TYPE CONTINUOUS MINING MACHINES Filed Nov. 18, 1952 INVENTOR ATTORNEY BURSTER ELEMENT FGR BQRING TYPE CONTENUOUS MINING NACEHNES Ger-aid H. van troh, Huntington, W. Va., assignor to Bituminous Coal Research, Inc, Washington, D. C., a corporation of Delaware Application November 18, B52, Serial No. 321,162

11 Claims. ((Il. 262-9) This invention relates to an improvement in bursters. More particularly, it is directed toward a bursting element to be used in a continuous mining machine of the rotary type such as disclosed in my copending joint application, Serial No. 229,438, filed May 23, 1951. This application is a continuation-in-part of my copending application Serial No. 257,879 filed November 23, 1951, now abandoned.

It is to be understood that the instant invention relates only to the burster per se, the other elements of the continuous mining machine used in conjuncion therewith and as disclosed and described herein being the co-invention described and claimed in said application.

It is an object of this invention to provide a burster which, in performing its function of fracturing coal or other mined products, performs that function without exercising a shear effect against the face.

It is a further object of the invention to provide a burster having a spiral construction along the slant height thereof of such design as to eifectively exert a constant hammering effect or repeated application of stress against the side walls of the bore during rotation of the burster, this hammering elTect enabling the coal to be efiectively broken when the burster is employed in conjunction with a continuous mining machine of the described type.

An additional object of the invention is to provide a burster which is essentially simple in construction and yet may be fabricated at low cost. Furthermore, the burster comprising my invention is designed for ease of removal or replacement upon the rotor housing of continuous mining machines utilizing the rotor principle or for optional use with machines of the cutter disc or cutter chain type.

With these objects and advantages in view, reference is now made to the drawings wherein the invention is more particularly disclosed and wherein:

Figure l is a side elevation view of the burster comprising the invention in position between the arms of a continuous mining machine rotor;

Figure 2 is a front elevation view of the invention as shown in Figure 1;

Figure 3 is a section view taken on the line 33 of Figure 1;

Figure 4 is an enlarged section view of a portion of the spiral of the burster;

Figure 5 is an enlarged section view, similar to Figure 4, and showing a modification of the invention illustrated in Figure 4.

The burster comprising my invention is generally indicated at 1. As herein shown, it is mounted upon the forward face of a rotor housing 2, the latter being provided with two forwardly extending rotor arms 3 and 4 which are right angular extensions respectively of two rotor shanks 5 and 6. These shanks are adapted for reciprocal movement in and out of the rotor casing 3 and also for rotary movement on the casing 2 when the latter is rotated by some power source such as the drive shaft 7. v

It will be seen that the shanks 5 and 6 are each posi- 2,239,798 Patented Mar. 27, 1956 tioned in suitable apertures or bores 9, each of which is provided with side gibs 10 and front gibs 11, the said gibs being adjustable in the manner described in the aforesaid application, Serial No. 229,438. As therein set forth, these shanks 5 and 6 may be driven outwardly or inwardly through the use of a worm which is engaged with two worm wheels 16 and 17. The latter rotate screw members in such manner that on one direction of rotation, the shanks 5 and 6 are extended and on a reverse direction of rotation, they are retracted.

These rotor arms 3 and 4 may be each provided with stationary bits 20 or rotary bits 21. Ordinarily only one type would be used in the mining operation. The arms are also provided with button bits and stud bits 26 which enable enlargement of the kerf to a suflicient size to facilitate turning of the mining machine while mining, or to prevent binding during any mining operation.

All of the foregoing description with relation to the continuous mining machine and the location of the burster with respect to the two rotor arms, as well as the mechanism to extend and retract these arms, is disclosed in my copending application, Serial No. 229,438, and forms no part of the invention disclosed and claimed herein.

Referring now particularly to the bursting screw 1, it will be seen that the burster comprises a conical base member 30. At the apex of the cone, the base member terminates into an extension 31, apertured as indicated in Figure 3 to receive a bit holding nut 32 and complementary bolt 34. This nut is adapted to engage a bit 35 through an appropriate aperture, the bit, of course, extending forwardly of the burster. The bit 35 is comprised of two angularly bent portions 36 and 38 which are pointed on their terminal ends to perform the function of initial cutting or boring into the face The burster at its opposite end is mounted upon a plate 40 by welding such as indicated at 41,- or any other suitable method of fixture thereto. This plate 40 is, in turn, positioned upon the front face of the rotor casing 2 through the medium of a series of bolts 42. Thus, the burster may be easily removed for replacement or repair simply by removal of the aforesaid bolts 42. I

The conical base member 39 may be hollow, the slant height or tapering side walls of the cone being of sufficient thickness to lend durability and operational strength to the rest of the structure. The outer surface of the cone is provided with a spiral or screw formation which continues from the forwardly extending element 31 to a position adjacent the burster base 40.

The spiral may be cast, turned, or otherwise fabricated in one piece with the base member 3i) or it may be made of steel or relatively hard and durable material, suitably shaped, and welded along the exterior surface of the cone. In any event, this spiral is also of unique construction in that the top portion 51 thereof is relatively fiat and of substantial thickness. This top portion 51 of the spiral formation 50 is formed in the preferred embodiment'of the invention shown in Figure 4, so as to be in parallel relationship with the longitudinal axis or altitude of the cone. Referring to Figure 4 it is seen that the spiral Si) is rectangular, or approximately rectangular, in cross section with top 51 and bottom 52 in parallel relationship. The sides and 71 are also parallel to each other. When disposed as shown in Figure 4 only one corner of the spiral 59 contacts the external surface of the cone. The spiral is thus positioned so that the top surface 51 is parallel to the longitudinal axis or altitude of the cone. It is welded in this position upon one side at 61 and also upon the opposite side thereof as at 60. The latter weld is larger than Weld 61 since it must fill the wedge-shaped the cone 3%. It will be appreciated that in constructions of simply the screw type the top edges of the spiral are not parallel to the axis of the screw. Also, in typical screw formations the terminal edges of the spiral are sharp, or relatively knife edged, rather than flat and cut or shear rather than effectuate a lateral thrust when such screw formations are moved forwardly in the kerf.

As an alternate embodiment of the invention, reference is. made to Figure 5 hereof. In this construction the spiral is shown as having a negative rake on its top surface 89, such surface being inclined downwardly from the face 71 of the spiral. The preferred angularity of surface 84) from the longitudinal axis of the cone is from 5 to 15 In Figure 5, this stated angle of inclination is indicated at A and is shown as approximately 15. The purpose of making the burster of this invention with a spiral haying flat, substantial surfaces, if or 3%), either parallel to or angular downwardly and rcarwardly to the longitudinal axis of the cone respectively will be further referred to hereinafter.

In the preferred embodiment of this invention, 1 have found a preferred angularity of slant height of the cone with respect to the longitudinal axis thereof. This preferred angularity approximates 15 to 20 and in the embodiment of the invention here shown and described, such angularity is approximately 17. Within this range of angularity, the desired pitch, based upon any given rate of advance, may be easily computed. Also, in the embodiment of the invention herein described, the ratio of thickness of the spiral to height thereof above the surface of the cone is preferably in the neighborhood of l to 3. This preferred ratio facilitates conveyance or transfer of the coal chips from the cutting bit rearwardly.

It has been found that the pitch of such spirals 55 should be an amount which approximates four times the rate of advance thereof. In actual use of the mechanism of this invention, the rate of advance has been computed at /2 per revolution. Thus, such pitch is normally 2". In any event, in the preferred embodiment of the invention, the pitch angle does not exceed 15 It will thus be appreciated that the burster is formed with a relatively low pitch.

This bursting element is also novel in that the spirals are throughout of constant pitch. As stated, the spiral element 50 is fiat upon its outer surface and formed with edges 51 of uniform configuration and either parallel or angular downwardly andrearwardly to the longitudinal axis of the cone. This enables the burster to exert a hammering elfect, or repeated application of stress, upon the side of the bore due to an alternating pressure as each spiral passes a given point, and pressure release as each spiral passes said point. For example, when the fiat spiral engages the face, a pressure of as much as 500,000 lbs. p. s. i. may be exerted upon a given point in the side of the bore; as the spiral passes such given point, this relatively high pressure is suddenly and drastically reduced be practically a zero pressure. The resultant action of the burster is a successive working effect which, in conjunction with the cutting action of the rotor arms, or in conjunction with cutter discs or cutter chains in machines employing these for the cutting action, causes an effective breakdown of the coal. This construction, with the flat pressure surfaces of the spiral. 50, is in sharp contrast to a purely screw type of element having sharp edged screw threads or spirals of increasing pitch. The latter can not obtain the same hammering or working effect heretofore described. Bursters of simply screw configuration exert merely a shear elfect upon the sides of the kerf or bore, lack in operation the hammering effect referred to, and, therefore, do not efficiently perform the bursting function. This is due to the sharp edges of the threads or spiral element, to the increasing pitch common to the purely screw type of burster, and the lack of an effective and substantial working face on the top portion of the spiral.

The hammering effect in the burster, as described in the foregoing, is aided materially by aflixing the spiral on the cone in such manner that the outer edge, 51 or 80, thereof is maintained either in parallel relationship with the longitudinal axis of the cone or in angular relationship with respect thereto. In the latter case the angularity is downwardly from front to rear. By so disposing the spiral it loses the inherent tendency common to any simple screw formation, such as found in bursters of the prior art, to penetrate the face of the coal by a shearing effect. it has been found that the top edge 51 of the spiral presents a substantial and effective surface, which during alternate periods of pressure and release as the cone is rotated, exerts alternate periods of lateral thrust against the sides of the bore thus causing rapid breakdown and fracture of the coal. It is to be understood that a primary purpose of making the fiat top portion of the spiral either parallel or angular from front to baclc downwardly with respect to the axis of the cone is to keep the bearing stress per square inch imposed on the coal to a minimum thereby eliminating local failure of the coal prior to gross fracture of the material between the bore and the cute extremity of the lierf.

The instant invention excludes to a minimum degree the amount of shear involved during rotation ofthe burster and provides to a maximum degree for a continual and effective hammering of the side walls of the bore. When this burster is used in conjunction with a continuous rotary mining machine of the described type, or with the cutter chain or cutter disc type of mechanism, it will be found that the hammering pulsations of the burster are complementary to the cutting motion of such mechanisms. The conjoint effect produces a quick and complete serration of the face, cracking the coal into the desired consistency.

The scope of this invention is not to be limited by any departure from the disclosure hereof, except as defined by the following appended claims.

I claim:

1. A burster element for continuous mining machines comprising a cone, said cone tapering forwardly toward a bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being provided with a spiral element, the intersection of said spiral element and a plane passing through said longitudinal axis of the cone defining surfaces having substantially straight side edges and a substantially flat top edge, the extension of said top edge not intersecting said longitudinal axis forwardly of said element.

2. A burster element for continuous mining machines comprising a cone, said cone tapering forwardly toward a bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being provided with a spiral element, the intersection of said spiral element and a plane passing through said longitudinal axis of the cone defining surfaces having substantially straight side edges and a substantially flat top edge, the extension of said top edge not intersecting said longitudinal axis forwardly of said element, said surface being disposed at an angle of from 15 to 20 to said longitudinal axis.

3. A burster element for continuous mining machines comprising a cone, said cone tapering forwardly toward a bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being pro vided with a spiral element, the intersection of said spiral element and a plane passing through said longitudinal axis of the cone defining surfaces having substantially straight side edges and a substantially flat top edge, the extension of said top edge not intersecting said longitudinal axis forwardly of said element, said spiral element being of constant pitch from the apex to the base of said cone.

4. A burster element for continuous mining machines comprising a cone, said cone tapering forwardly toward a bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being provided with a spiral element, the intersection of said spiral element and a plane passing through said longitudinal axis of the cone defining surfaces having substantially straight side edges and a substantially fiat top edge, said top edge having a substantial working face, the extension of said top edge not intersecting said longitudinal axis forwardly of said element, said exterior surface being disposed at an angle of from 15 to 20 to said longitudinal axis, said spiral element being of constant pitch from the apex to the base of said cone.

5. A burster element adapted for rotation on continuous mining machines comprising a hollow cone, said cone tapering to a bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being provided with a spiral element, the intersection of said spiral element and a plane passing through the longitudinal axis of the cone defining surfaces having substantially straight side edges and a substantially flat top edge, the extension of said top edge not intersecting said longitudinal axis forwardly of said element, said surface being disposed at an angle of from 15 to 20 to said longitudinal axis, said spiral element being of constant pitch from the apex to the base of said cone, said top edge being parallel to said axis and said pitch being an amount approximating four times the rate of advance of said cone per revolution thereof.

6. A burster element for continuous mining machines comprising a cone, said cone tapering forwardly toward a bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being provided with a spiral element, the intersection of said spiral element and a plane passing through said longitudinal axis of the cone defining surfaces having substantially straight side edges and a substantially flat top edge, said top edge having a substantial working face, the extension of said top edge not intersecting said longitudinal axis forwardly of said element, said surface being disposed at an angle of from 15 to 20 to said longitudinal axis, said spiral having a pitch angle of less than 15 7. A burster element for continuous mining machines comprising a cone, said cone tapering forwardly toward a bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being provided with a spiral element, the intersection of said spiral element and a plane passing through said longitudinal axis of the cone defining surfaces having substantially straight side edges and a substantially flat top edge, the extension of said top edge not intersecting said longitudinal axis forwardly of said element, said surface being disposed at an angle of from 15 to 20 to said longitudinal axis, said spiral element being of constant pitch from the apex to the base of said cone, and having a pitch angle of less than 15 said pitch being an amount approximating four times the rate of advance of said cone per revolution thereof.

8. A burster element for continuous miningmachines comprising a cone, said cone tapering forwardly toward a straight side edges and a substantially flat top edge, the extension of said top edge not intersecting said longitudinal axis forwardly of said element and from said bit holding element rearwardly and downwardly being disposed at an angle to said longitudinal axis of from 0 to 15.

9. A burster element for continuous mining machines comprising a cone, said cone tapering forwardly toward a bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being provided with a spiral element, the intersection of said spiral element and a plane passing through said longitudinal axis of the cone defining surfaces having substantially straight side edges and a substantially flat top edge, the extension of said top edge not intersecting said longitudinal axis forwardly of said element, said surface being disposed at an angle of from about 15 to 20 to said longitudinal axis, said spiral element having a pitch angle of less than 15, said top extending rearwardly with respect to said bit holding element and downwardly toward said axis at an angle of from about 5 to 15 to said longitudinal axis.

10. A burster element for continuous mining machines comprising a hollow cone, said cone tapering forwardly toward a bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being provided with a spiral element, the intersection of said spiral element and a plane passing through said longitudinal axis of the cone defining surfaces having substantially straight side edges and a substantially fiat top edge, the extension of said top edge not intersecting bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being provided with a spiral element, the intersection of said spiral element and a plane passing through said longitudinal axis of the cone defining surfaces having substantially said longitudinal axis forwardly of said element, said surface being disposed at an angle of from about 15 to 20 to said longitudinal axis, said spiral element being of constant pitch from the apex to the base of said cone, said top edge extending rearwardly with respect to said bit holding element and downwardly toward said axis at an angle of from about 5 to 15 to said longitudinal axis.

11. A burster element for continuous mining machines comprising a hollow cone, said cone tapering forwardly toward a bit holding element in alignment with the longitudinal axis thereof, the exterior surface of said cone being provided with a spiral element, the intersection of said spiral element and a plane passing through said longitudinal axis of the cone defining surfaces having substantially straight side edges and a substantially fiat top edge, the extension of said top edge not intersecting said longitudinal axis forwardly of said element, said surface being disposed at an angle of from about 15 to 20 to said longitudinal axis, said spiral element having a pitch angle of less than 15 and being of constant pitch from the apex to the base of said cone, said top edge extending rearwardly with respect to said bit holding element and downwardly toward said axis at an angle of from about 5 to 20 to said longitudinal axis.

References Cited in the file of this patent UNITED STATES PATENTS 279,962 Mayes June 26, 1883 874,028 Newcome Dec. 17, 1907 1,445,085 Joy Feb. 13, 1923 2,562,841 Compton July 11, 1951 

